【作者】 陆万顺；

【导师】 符云清；

【作者基本信息】 重庆大学 ， 计算机系统结构， 2011， 硕士

【摘要】 SIP(Session Initial Protocol)是伴随着互联网的发展而诞生和发展的,并以其简单易用以及良好的扩展性和开放性等优势,已发展成为下一互联网至关重要的应用协议。SIP本身缺乏相应有效的安全机制。现有SIP安全机制普遍存在一定的使用局限性和安全漏洞,并且会带来如服务器负担过重之类的负面影响,从而降低SIP的服务效率和质量,会影响SIP会话网络的安全性和稳定性。同时,SIP的承载运行环境将是高度开放并且分布式异构的下一代互联网,具有很大不确定性和不可靠性,这将给SIP相应功能安全、可靠实现带来极大的隐患。高效、便捷的SIP安全机制对于SIP进一步的发展和推广应用具有十分重要的意义。SIP安全机制必须从协议本身入手,并结合下一代互联网的特殊性全方位地进行考虑,同时要保持下一代互联网的整体性和一致性等特性。本文首先详细研究了SIP相关重要概念和属性,重点分析了SIP消息规范,包括SIP请求消息和响应消息;随后对SIP安全威胁以及现有IP安全机制进行了详细分析,主要分析了注册劫持、服务器伪装、消息篡改和拒绝服务等安全问题,并对现有的SIP安全认证和加密方式进行了综述,包括HTTP摘要认证、基于身份的安全认证、S/MIME加密、TLS加密、IPSec加密。在此基础上,研究了基于ECDH算法的轻量级SIP安全认证以及密钥协商机制,并引入一次口令机制,提出了基于ECODH的安全验证和密钥协商机制,对其进行了安全性论证,并与现有的RSA加密、DH密钥协商分析对比证明了其高效的轻量特性;同时本文还借鉴了IP路由器利用能力标记选择数据来防御DoS/DDoS的思想,在每个SIP网络域设置边界代理服务器对SIP消息执行“能力”分析处理,对所有过往的SIP消息全程监控和预警,以更好地防御DoS/DDoS安全威胁。这里的“能力”是指边界代理服务器选择处理SIP消息行为的参照依据,包括了符合SIP消息行为特征的相关安全属性与鉴别准则。本文提出的SIP安全机制更安全、高效和轻便,它解决了ECDH验证和密钥协商用户密码容易被窃取的风险,协商密钥较为简洁,实现过程便捷,并且更为完备地符合标准安全性评估规范。同时,本文引入“能力”标签,对过往SIP消息进行全程监控和预警,变被动防御为主动防御,能更为智能化地对不合法的SIP消息进行过滤,有效抵制DoS/DDoS。另外,对SIP网络拓扑轻量化地优化,便于SIP功能更为快捷地实现。更多还原

【Abstract】 SIP was brought up and develops along with the Internet development, it has become a critical application protocol for the NGN(Next Generation Network)due to its advantage of simple structure with better extensibility and openness, and its convenience to be carried out. However, SIP has no corresponding effective security mechanism on its own. The existing security mechanisms for SIP have some certain limitations and security vulnerabilities universally. Moreover, these security measures will also bring some negative impacts, such as much heavier burdens for SIP servers during the connections and business process, reducing the efficiency and quality of services through SIP, affecting the security and stability of the SIP Session Network. Meanwhile, the loadbearing circumstance for SIP to run is a highly open and distributed application environment with great uncertainty and unreliability, resulting in serious latent security risks for the corresponding function safely and reliably achieving of SIP. So, an efficient and convenient security mechanism is very important for the further development and application for SIP.The security mechanism for SIP should be comprehensively considered combining the intrinsic characteristics of protocol itself and the particularity of NGN, maintaining its consistency, integrity and other special features. In this paper, we firstly discuss the important concepts and attributes of SIP, focusing on the specification of SIP message, including the request message and response message of SIP. Secondly,we make classified research about the existing security threats and mechanisms of SIP in detail, such as registration hijacks, server disguising, message tampering, DoS(Denial of Service) and so on, and give detailed study and analysis on existing SIP security authentication and encryption, including HTTP digest authentication, identity-based security authentication, S/MIME encryption, TLS encryption, IPSec encryption. Thirdly, we study an advanced lightweight security authentication and key negotiation mechanism based on ECDH algorithm, in which one-time password authentication, and a new authentication and key negotiation method based on ECODH are introduced. Subsequently , we demonstrate its properties of security according to the Key Negotiation Security Properties Standard. It shows the highly lightweight characteristics of the new protocol by comparison the amount of its calculation with existing RSA encryption, DH key agreement. As we know, the DoS/DDoS defense for IP networks benefits from the capabilities signing during the data selection in routers. In this paper, we combine the instinct characteristics of SIP and the achievement of credibility research for NGN, configuring boundary proxy servers in every SIP network domain to perform capabilities analysis and process to SIP messages, monitoring and prewarning them simultaneously during the whole procedure to well defending DoS/DDoS. Besides, we also improve the topology of SIP network to improve the overall implementation in a lightweight pattern. The capabilities are used for boundary proxy servers to choose the coming SIP messages as the standard reference, including security attributes and identification strategies associated with the SIP message behavioral characteristics.Based on the above research work, we proposed a more appropriate capabilities-based and lightweight security scheme for SIP, which is more suitable for its further applications in NGN. Comparing to the existing SIP security mechanisms, it is more secure, efficient and portable. The proposed solution is able to avoid the risks of user password being easily stolen for the authentication and key agreement process based on ECDH, and it is characterized of more concise consultation key, easy-to-realization, and conforming to the security assessment specifications perfectly. Also, for our solution monitoring and prewarning SIP messages through capabilities analysis procedure during the whole process, it transforms passive defense into active defense, filtering illegitimate SIP messages more intelligently, and thus defensing DoS/DDoS effectively. Additionally, the lightweight optimization for SIP network topology will make implementation of SIP functions easier and more efficient.更多还原